COEXISTENCE OF ANTIFERROMAGNETIC ORDER AND SUPERCONDUCTIVITY WITH T-NHIGHER THAN T-C IN DYNI2B2C

A superconducting transition temperature T-c of 3.8 K with an onset as high as 5.2-5.5 K was reported for quaternary borocarbide DyNi2B2C wi th a high antiferromagnetic Neel temperature T-N around 10.1-10.8 K. N o reentrant behavior was observed down to 0.3 K demonstrating a perfec t coexistence between superconductivity and antiferromagnetic order. A superconducting upper critical field H-c2(0) of 3.0 kG, lower critica l field H-c1(0) of 200 G and a Ginzburg-Landau parameter K of 3.7 were derived. A broad T-c transition points to a possible small T-c varyin g homogeneity range of DyNi2-alphaB2-betaC1-delta in the phase diagram . The magnetic entropy S-m of 10.3 J/mol K or 90% Rln 4 indicates anti ferromagnetic ordering of Dy3+ with a quadruplet ground state in the t etragonal crystal field. Two field-induced weak-ferromagnetic-like tra nsitions with a field of around 1 T were observed at 2 K.